The present invention relates to pressure or force operated latching mechanisms and high pressure systems using the same. More particularly, the present invention relates to an improved latching device which actuates an electrical switch, or valve, or an engine throttle, at a given pressure or force level, and which deactivates at another and different and independent pressure force level, or visa versa, and to high pressure systems using such latching devices.
There are many engineering applications where it is necessary to provide a pressure or force responsive device which operates and is responsive at two different pressure or force levels to control another device such as a valve, or an engine throttle, or an electrical switch, for example. One typical such application is in high pressure spray systems where a motor operates a pump to provide the high pressure. In such a system as long as the spray or stream is being generated, the pump is operated by the motor to maintain the desired pressure level. When the spray or stream is no longer being dispensed, it is desirable to run the pump only until a desired pressure level is reached and thereafter, when the sprayer is operated, to actuate the pump to provide the proper spray pressure This may also be accomplished by actuating a by-pass valve when the system pressure exceeds a predetermined value and deactivates the by-pass valve when the pressure is below a certain level. Another typical application of the improved latching mechanism of the present invention is in the control of air compressors driven by an electrical motor or some other power source. By way of example, an air compressor for producing "shop air" would normally include a tank holding air at about 150 psig. As air is used from the tank and the pressure reduced to about 60 psig, for example, the compressor is operated to bring the tank pressure back up to 150 psig at which time the compressor, usually motor driven, is turned off.
Heretofore, it has been difficult to obtain the desired control of such a pressure system, within two different pressure levels for a start-stop sequence, by the use of the common type of pressure switch employing a non-linear element such as a Bellville spring. This is especially true where there is a wide range between start or cut-on and stop or cut-off, since the operating range of a Bellville type of spring operated device is limited.
By contrast, the latching device of the present invention affords an unlimited range between the desired cut-on and cut-off levels, by the use of a common type of coil spring, and thus does not rely upon the limited range of operation normally associated with non-linear mechanical elements normally used in conventional pressure of force actuated devices of the prior art.
Another advantage of the present invention is that the length of the stroke may be made quite long without unduly complicating the design or affecting performance of the device. This unique characteristic of the device of this invention makes it relatively simple to design a latching mechanism to operate the levers and/or throttle valve of an internal combustion engine. Thus, where an internal combustion engine is used to drive a pump or compressor, the latching mechanism of this invention may be used both to control the throttle setting of the engine and to operate a fluid control valve. In situations requiring an intermittent demand, once the required pressure level is reached, the latching mechanism of this invention actuates a bypass valve thus preventing an excessive pressure build-up and simultaneously throttles back the engine to an idling position. This mode of operation prevents excessive build-up of heat in the pump fluid and also reduces engergy consumption by allowing the internal combustion engine to idle during the no load phase.